# CVE-2026-66276: Apache Qpid Proton-J: Unbounded disposition range handling can lead to denial of service

> An authenticated attacker can cause denial of service in Apache Qpid Proton-J by sending crafted disposition frames with large ranges.

- **Severity:** Medium 6.5 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 5 Aug 2026
- **Updated:** 6 Aug 2026
- **Also known as:** CLEANSTART-2026-JV92221, GHSA-jx9q-477g-4wgw

## What is CVE-2026-66276?

CVE-2026-66276 is a medium-severity denial of service vulnerability in Apache Qpid Proton-J, published on 5 Aug 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

An authenticated attacker can craft a disposition frame with large or illegal ranges causing excessive CPU usage due to naive range handling, leading to denial of service.

This issue affects Apache Qpid Proton-J: through 0.34.1.

Users are recommended to upgrade to version 0.35.0, which fixes the issue.

Weakness: CWE-606 (Unchecked Input for Loop Condition)

## Which versions are affected by CVE-2026-66276?

It affects 1 product.


Products: Apache Qpid Proton-J.

## How do I fix CVE-2026-66276?

Upgrade to a fixed version.

## Is CVE-2026-66276 being exploited?

There is no known exploitation of CVE-2026-66276 in the wild and no public exploit code.

## Other vulnerabilities in Apache Qpid Proton-J

- [CVE-2026-66257](https://insights.sbomify.com/CVE-2026-66257/): Apache Qpid Proton-J: Unbounded symbol value caching can lead to pre-authentication resource exhaustion (high 7.5)
- [CVE-2026-66273](https://insights.sbomify.com/CVE-2026-66273/): Apache Qpid Proton-J: Type size/count handling can lead to excessive allocation pre-authentication (high 7.5)
- [CVE-2026-66274](https://insights.sbomify.com/CVE-2026-66274/): Apache Qpid Proton-J: Unbounded type nesting can lead to pre-authentication stackoverflow (high 7.5)
- [CVE-2018-17187](https://insights.sbomify.com/CVE-2018-17187/): Improper Certificate Validation in proton-j (high 7.4)
- [CVE-2026-66275](https://insights.sbomify.com/CVE-2026-66275/): Apache Qpid Proton-J: Incoming session flow control window can be exceeded (medium 6.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-66276 and fix it if it is affected.

What it is: CVE-2026-66276 is a medium-severity denial of service vulnerability in Apache Qpid Proton-J, published on 5 Aug 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-66276 in the wild and no public exploit code.

Affected product: Apache Qpid Proton-J. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-66276/ (Markdown: https://insights.sbomify.com/CVE-2026-66276/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-66276
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-66276
- OSV: https://osv.dev/vulnerability/CVE-2026-66276

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-66276/
Summaries are generated and may contain mistakes; the official description above is the record.